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18041. YSOs in DROXO (Deep rho Oph XMM obs.)
ID:
ivo://CDS.VizieR/J/A+A/519/A34
Title:
YSOs in DROXO (Deep rho Oph XMM obs.)
Short Name:
J/A+A/519/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-rays from very young stars are powerful probes to investigate the mechanisms at work in the very first stages of the star formation and the origin of X-ray emission in very young stars. We present results from a 500ks long observation of the rho Ophiuchi cloud with a XMM-Newton large program named DROXO, aiming at studying the X-ray emission of deeply embedded young stellar objects (YSOs).
18042. YSOs in Herschel-Hi-GAL survey
ID:
ivo://CDS.VizieR/J/A+A/549/A130
Title:
YSOs in Herschel-Hi-GAL survey
Short Name:
J/A+A/549/A130
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Herschel survey of the Galactic plane (Hi-GAL) provides a unique opportunity to study star formation over large areas of the sky and different environments in the Milky Way. We use the best-studied Hi-GAL fields to date, two 2{deg}x2{deg} tiles centered on (l,b)=(30{deg}, 0{deg}) and (l,b)=(59{deg},0{deg}), to study the star formation activity in these regions of the sky using a large sample of well-selected young stellar objects (YSOs). We used the science demonstration phase Hi-GAL fields, where a tremendous effort has been made to identify the newly formed stars and to derive their properties as accurately as possible, e.g. distance, bolometric luminosity, envelope mass, and stage of evolution. We estimated the star formation rate (SFR) for these fields using the number of candidate YSOs and their average time scale to reach the zero age main sequence, and compared it with the rate estimated using their integrated luminosity at 70um, combined with an extragalactic star formation indicator.
18043. YSOs in LDN 1641 with Hectochelle spectra
ID:
ivo://CDS.VizieR/J/ApJS/207/5
Title:
YSOs in LDN 1641 with Hectochelle spectra
Short Name:
J/ApJS/207/5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the young stellar objects (YSOs) in the Lynds 1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, the Two Micron All Sky Survey, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted a sub-sample of YSOs for optical spectroscopy with the MMT/Hectospec and the MMT/Hectochelle. We use these data, along with archival photometric data, to derive spectral types, extinction values, masses, ages, and accretion rates. We obtain a disk fraction of ~50% in L1641. The disk frequency is almost constant as a function of stellar mass with a slight peak at log (M_*_/M_{sun}_){approx}-0.25. The analysis of multi-epoch spectroscopic data indicates that the accretion variability of YSOs cannot explain the two orders of magnitude of scatter for YSOs with similar masses. Forty-six new transition disk (TD) objects are confirmed in this work, and we find that the fraction of accreting TDs is lower than for optically thick disks (40%-45% versus 77%-79%, respectively). We confirm our previous result that the accreting TDs have a median accretion rate similar to normal optically thick disks. We confirm that two star formation modes (isolated versus clustered) exist in L1641. We find that the diskless YSOs are statistically older than the YSOs with optically thick disks and the TD objects have a median age that is intermediate between those of the other two populations. We tentatively study the star formation history in L1641 based on the age distribution and find that star formation started to be active 2-3 Myr ago.
18044. YSOs in 9 LMC star forming regions
ID:
ivo://CDS.VizieR/J/A+A/542/A66
Title:
YSOs in 9 LMC star forming regions
Short Name:
J/A+A/542/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We introduce a new set of selection criteria for the identification of infrared bright young stellar object (YSO) candidates and apply them to nine HII regions in the Large Magellanic Cloud (LMC), focusing particularly on lower mass candidates missed by most surveys. Data are from the Spitzer Space Telescope legacy program SAGE (Surveying the Agents of Galaxy Evolution; Meixner et al. 2006, Cat. J/AJ/132/2268, see also II/305), combined with optical photometry from the Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 1997AJ....114.1002Z) and near-infrared photometry from the InfraRed Survey Facility (IRSF; Kato et al. 2007, Cat. II/288). We choose regions of diverse physical size, star formation rates (SFRs), and ages. We also cover a wide range of locations and surrounding environments in the LMC. These active star-forming regions are LHA 120-N 11, N 44, N 51, N 105, N 113, N 120, N 144, N 160, and N 206. Some have been well-studied (e.g., N11, N44, N160) in the past, while others (e.g., N51, N144) have received little attention. We identify 1045 YSO candidates, including 918 never before identified and 127 matching previous candidate lists. We characterize the evolutionary stage and physical properties of each candidate using the spectral energy distribution (SED) fitter of Robitaille et al. (2007ApJS..169..328R) and estimate mass functions and SFRs for each region.
18045. YSOs in L1630N and L1641
ID:
ivo://CDS.VizieR/J/A+A/504/461
Title:
YSOs in L1630N and L1641
Short Name:
J/A+A/504/461
Date:
21 Oct 2021
Publisher:
CDS
Description:
Knowledge of the evolution of circumstellar accretion disks is pivotal to our understanding of star and planet formation; and yet despite intensive theoretical and observational studies, the disk dissipation process is not well understood. Infrared observations of large numbers of young stars, as performed by the Spitzer Space Telescope, may advance our knowledge of this inherently complex process. While infrared data reveal the evolutionary status of the disk, they hold little information on the properties of the central star and the accretion characteristics. Existing 2MASS and Spitzer archive data of the Lynds 1630N and 1641 clouds in the Orion GMC provide disk properties of a large number of young stars. We wish to complement these data with optical data that provide the physical stellar parameters and accretion characteristics.
18046. YSOs in N63 and N180
ID:
ivo://CDS.VizieR/J/ApJ/678/200
Title:
YSOs in N63 and N180
Short Name:
J/ApJ/678/200
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used Spitzer infrared observations to find the young stars of two HII regions in the Large Magellanic Cloud, N63 and N180. The young stellar object (YSO) candidates were identified in each nebula by means of color-color, color-magnitude diagrams, and the shapes of their spectral energy distributions (SEDs). The most luminous YSOs are found near the ionization fronts within strong 8um emission clumps. Most YSOs, less luminous, are seen in projection inside the HII regions. HST images show several Class I stars that have emerged along the borders of the HII regions; other YSOs are embedded in cometary clouds. The most luminous YSO of N63 is connected to a string of pointlike sources. Its SED can be modeled by a central source of stellar mass M_*_ between 7 and 11M_{sun}_, with a circumstellar disk of outer radius R_d_ of ~55AU, and an envelope of moderate accretion rate, M_env_ of ~2x10^-5^M_{sun}_/yr. N180 is experiencing a phase of star formation more intense than N63, attested by the properties of its most luminous YSO: M_*_ of 25M_{sun}_, R_d_ of ~200AU, and M_env_ of ~1.5x10^-3^M_{sun}_/yr. The modes of triggered star formation in N63 and N180 appear similar to those seen in Galactic HII regions.
18047. YSOs in star-forming region associated to V582 Aur
ID:
ivo://CDS.VizieR/J/MNRAS/468/2325
Title:
YSOs in star-forming region associated to V582 Aur
Short Name:
J/MNRAS/468/2325
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have studied the environment of the FU Ori type star V582 Aur. Our aim is to explore the star-forming region associated with this young eruptive star. Using slitless spectroscopy, we searched for H{alpha} emission stars within a field of 11.5 arcmin x 11.5 arcmin, centred on V582 Aur. Based on UKIDSS and Spitzer Space Telescope data, we further selected infrared-excess young stellar object candidates. In all, we identified 68 candidate low-mass young stars, 16 of which exhibited H{alpha} emission in the slitless spectroscopic images. The colour-magnitude diagram of the selected objects, based on the IPHAS data, suggests that they are low-mass pre-main-sequence stars associated with the Aur OB 1 association, located at a distance of 1.3kpc from Sun. The bright-rimmed globules in the local environment of V582 Aur probably belong to the dark cloud LDN 1516. Our results suggest that star formation in these globules might have been triggered by the radiation field of a few hot members of Aur OB 1. The bolometric luminosity of V582 Aur, based on archival photometric data and on the adopted distance, is 150-320L_{sun}_.
18048. YSOs in the central 400pc of the Galaxy
ID:
ivo://CDS.VizieR/J/ApJ/702/178
Title:
YSOs in the central 400pc of the Galaxy
Short Name:
J/ApJ/702/178
Date:
21 Oct 2021
Publisher:
CDS
Description:
The central kpc of the Milky Way might be expected to differ significantly from the rest of the Galaxy with regard to gasdynamics and the formation of young stellar objects (YSOs). We probe this possibility with mid-infrared observations obtained with Infrared Array Camera and Multiband Imaging Photometer on Spitzer and with Midcourse Space Experiment. We use color-color diagrams and spectral energy distribution (SED) fits to explore the nature of YSO candidates (including objects with 4.5um excesses possibly due to molecular emission). We use the SEDs of these sources to estimate their physical characteristics; their masses appear to range from ~10 to ~20M_{sun}_.
18049. YSOs in the Galactic HII region Sh2-297
ID:
ivo://CDS.VizieR/J/ApJ/759/48
Title:
YSOs in the Galactic HII region Sh2-297
Short Name:
J/ApJ/759/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756/cm3 and 9.15x10^5^cm^-6^pc using the radio continuum observations at 610 and 1280MHz, and Very Large Array archival data at 1420MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~7.5'x7.5' centered on Sh2-297 using grism slitless spectroscopy (to identify the H{alpha} emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H-K>0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~0.1-2M_{sun}_ and 0.5-2Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be ~1Myr, which is of the order of dynamical age of 1.07Myr of the H II region. Using the estimated range of visual extinction (1.1-25mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.
18050. YSOs in the Gould Belt regions with Gaia-DR2 data
ID:
ivo://CDS.VizieR/J/ApJ/867/151
Title:
YSOs in the Gould Belt regions with Gaia-DR2 data
Short Name:
J/ApJ/867/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the astrometric results from the Gaia second data release (DR2) for young stellar objects (YSOs) in star-forming regions related to the Gould Belt (GB). These regions are Barnard 59, Lupus 1 to 4, Chamaeleon I and II, {epsilon} Chamaeleontis, the Cepheus flare, IC 5146, and Corona Australis. The mean distance to the YSOs in each region is consistent with earlier estimations, though a significant improvement in the final errors was obtained. The mean distances to the star-forming regions were used to fit an ellipsoid of size (358+/-7)x(316+/-13)x(70+/-4)pc^3^, centered at (X0,Y0,Z0)=(-82+/-15,39+/-7,-25+/-4)pc, consistent with recently determined parameters of the GB. The mean proper motions were combined with radial velocities from the literature to obtain the three- dimensional motions of the star-forming regions, which are consistent with a general expansion of the GB. We estimate that this expansion is occurring at a velocity of 2.5+/-0.1km/s. This is the first time that motions of YSOs have been used to investigate the kinematics of the GB. As an interesting side result, we also identified stars with large peculiar velocities.

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